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PremNandhini Satgunam, Eli Peli; Measuring Volume Scotoma in Bitemporal, Binasal and Central Field Loss. Journal of Vision 2011;11(15):61. doi: 10.1167/11.15.61.
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© ARVO (1962-2015); The Authors (2016-present)
Volume scotoma (blind areas projected in depth) is theoretically predicted from combining monocular visual fields. However, computation from monocular perimetry assumes known retinal fixation locus. Conventional perimeters (Humphrey and Goldmann) are not suitable to measure volume scotoma since the visual fields are mapped at the fixation plane. We developed methods to directly measure volume perimetry in cases of interest. Using computerized dichoptic perimeter and a fixation target in front of the screen a volume field behind fixation is measured. Such scotomas are expected in bitemporal (hemianopic) and in central field loss (CFL). Volume scotoma in front of fixation occurring with binasal and CFL can be measured using a transparent screen placed in front of the fixation and targets presented over it using a laser pointer. Measurements of volume fields are consistent showing scotomas behind fixation or in front, for bitemporal and binasal field loss, respectively, and a rapid shrinking scotoma behind closer fixation for patients with small CFL. With direct binocular measurements of volume scotoma no assumptions are needed. The measurements done binocularly demonstrate volume scotoma and if done dichopticaly can show each eye's contribution, and the results may have important implications for various daily activities.
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